1. Field of the Invention
The present invention relates to a Linux-based system having strengthened security, and more particularly to a method and a system for providing a security policy for downloaded applications in a security operating system.
2. Description of the Related Art
Presently, as the role of the Internet is extended from merely providing information to, or sharing information with intranet networks, electronic commerce, and the like, the need to protect against hacking is of increased importance. Hacking is an invasion of privacy, may cause the destruction of property, tarnish a corporation's image, compromise corporate trade secrets, interrupt service, and the like, and the scale of damage caused by hacking has been increasing at a high rate. Particularly, in the case of a corporation, whether the corporation can defend itself against hacking is vital to its survival.
Recently, with the development of the Internet, it has become possible to access personal computers and networks throughout the world. In such environments, the accessing of data from remote locations is convenient, but sensitive data may be exposed to unauthorized users, and malicious attacks may frequently occur. Accordingly, security technologies of application layers, such as encryption, firewalls, invasion detecting systems, and the like, for safe sharing and use of information have been developed to protect information of networks or servers. However, such security technologies of application layers have their own vulnerabilities and drawbacks such that it is difficult to cope with privacy violations by otherwise authorized users, misuse/abuse of authority, and attack through system hacking.
In order to solve this problem and to implement a Trusted Computing Base (TCB), research for a security operating system has been ongoing, and a representative security operating system may be SELinux (Security Enhanced Linux). SELinux is a security operating system developed by the National Security Agency (NSA) through application of a Flux Advanced Security Kernel (Flask) structure to Linux, and provides a structure that executes diverse access control policies, such as Type Enforcement (TE), role based access control, Multi-Level Security (MLS), and the like. SELinux also performs access control of not only files and device files but also various resources in the system, such as processes, signals, memory, and the like. SELinux also minimizes the range of damage through minimum authority allocation, and prevents the execution of malicious code. In structure, SELinux separates a policy decision module and a policy execution module from each other to provide flexibility to the security policy. On the other hand, a general UNIX operating system uses a Discretionary Access Control (DAC) method as an access control method. Also, in Trusted Computer System Evaluation Criteria (TCSEC), the same concept as the discretionary access control policy is defined as DAC. That is, a method of limiting the access of an object based on the discretion of the subject or a group to which the subjects belong is defined as DAC.
The biggest security problem in the DAC method is that the authority of a super user (i.e., root) is too great. That is, a super user can set all the environment variables of the system, and can delete all processes. Accordingly, once a hacker becomes a super user using a vulnerability, they can perform all the functions of a super user.
According to the DAC method, as many system files are changed or the kernel becomes larger and has many support functions, the kernel becomes modularized, and a part of the kernel performs a task after a module is inserted into the kernel. Accordingly, a serious problem may occur as malicious code is inserted into the kernel.
Although SELinux can perform more enhanced access control, there is a high possibility that, due to a type of a downloaded application that means a group having the same security attribute and Boolean designation, a special control element in SELinux policy controlling what part of policy is applied to an application, which are given during installation of the downloaded application, the given designation collides with the existing designation, and thus it is difficult for general users to set the security policy for the downloaded application to suit the users' purposes.